Probe structure and manufacturing method thereof

ABSTRACT

In a probe structure which has a bump contact protruded from one surface of an insulating substrate, the bump contact is deposited such that a surface roughness falls within a predetermined range specified by Rmax within a range from 0.01 to 0.8 mum, Ra within a range from 0.001 to 0.4 mum, and a ratio of Rmax/Ra within a range from 2 to 10. Such a surface roughness is realized by depositing a convex/concave layer formed by aggregation of fine grains. The convex/concave layer is directly deposited to a basic shape portion without any intermediate layer left between the convex/concave layer and the basic shape portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a probe structure for testing adevice-under-test (DUT), such as a semiconductor device, by a burn-intest or the like, and also to a method of manufacturing the probestructure. It is to be noted throughout the instant specification thatthe probe structure is electrically contacted with a contact object,such as an electrode pad or a circuit pattern, which is formed on theDUT and which may be simply called an electrode.

2. Description of the Related Art

In a conventional probe structure, a hemispherically projecting bumpcontact is formed as a contact point for contacting with the electrodeformed on the DUT, such as a semiconductor device.

As a bump contact having the conventional bump structure, it is known inthe art that fine projections are intentionally formed on a surface ofthe bump contact so as to improve reliability of contact with theelectrode (for example, Japanese Unexamined Patent Publication (A) No.H06-27141, namely, 27141/1994). By forming fine projections on thesurface of the bump contact, the contact area of the bump contact withthe electrode becomes large and this enables a reliable contact with theelectrode. Even when an oxide film is formed on the surface of thecontact object, namely, the electrode, the fine projections can breakthe oxide film, and give a stable contact resistance.

Another probe structure has been disclosed in Japanese Unexamined PatentPublication (A) No. H09-133711 (133711/1997) and has a structure similarto that shown in FIG. 1. Specifically, a bump contact 2 illustrated inFIG. 1 is protruded from one side or one principal surface of aninsulating substrate 1. The bump contact 2 is electrically connectedthrough a conductive portion 4 to an electrode 3 which is operable as apart of an electric circuit provided on the other side, namely, anotherprincipal surface of the insulating substrate. The bump contact 2 has abasic shape portion 2 a (an inside layer), of nickel, and anintermediate layer of plated gold on a surface of the basic shapeportion 2 a. In addition, a surface layer 2 c and fine projections 2 deach of which is formed by rhodium are deposited on the surface of thisintermediate layer. The surface layer 2 c and the fine projections 2 dmay preferably be formed by the same material (rhodium) deposited byplating. The fine projections 2 d are formed by controlling platingcurrent so as to be locally protruded from the surface layer 2 c. Withthis structure, the surface layer 2 c and the fine projections 2 d arecombined together to form an integrated material structure without aboundary between them. As a result, the above-mentioned publicationreports that fine projections are obtained which hardly come off andwhich are practically kept constant in configuration.

However, no disclosure is made at all in the above-referencedpublications about sizes and surface roughness of the fine projectionsformed on the surface of the conventional bump contact. From this fact,it is difficult from the publications to know about appropriate rangesfor the surface roughness specified by Rmax and Ra, a ratio of Rmax/Ra,and about a projection pitch or spacing, the projection shape includingthe thickness, the projection density and other configuration ofprojections. As a result, forming conditions are liable to fall outsideof an acceptable range and to give rise to undesirable shapes of theprojections. Since the forming method itself of projections makes itdifficult to avoid a variation of the projection shape, the projectionshape often falls outside the acceptable range. A projection shapeformed outside the acceptable range results in inconveniences, such asbreakaway of projections and a variation of contact resistance.

Alternatively, a method is also disclosed in Japanese Unexamined PatentPublication (A) No. H09-133711 (133711/1997) to manufacture a bumpcontact. The bump contact actually manufactured by the method isdisadvantageous in that adhesion of the surface layer 2 c and theprojections 2 d is weak and the projection shape or configuration isvariable. This is also similar to the case where no intermediate layer 2b of plated gold is interposed between the surface layer 2 c of rhodiumand the projections 2 d of rhodium and, as a result, the surface layer 2c and the projections 2 d are formed directly on the surface of thebasic shape portion 2 a.

Practically, it is confirmed that the surface layer 2 c and theprojections 2 d of rhodium in the bump contact manufactured by themethod disclosed in the aforementioned Publication have easily peeledoff in a tape peeling test. This shows a low adhesion of theprojections.

In the bump contact prepared by the method described in theabove-publication, as projections become high, they become thinner insome cases. This easily comes off the bump surface through repetition ofcontact between the bump contact and the contact object, and this bringsabout a variation in contact resistance.

Heretofore, it is difficult to deposit the fine projections always to aconstant height (a constant surface roughness) and to keep a variationof surface roughness and a projection density invariable. This sometimesresults in a variation of the contact resistance between differentbumps. If the contact resistance is varied among bumps, inconvenience isliable to occur on transmitting electric signals between the probestructure and the DUT. This makes it difficult to obtain accurate andreliable measurement results due to the variation of the contactresistance among the bumps. Very high contact resistance makes itdifficult to transmit and receive electric signals between the probestructure and the DUT.

As a result of searching for causes of the above circumstances, it hasbeen ascertained that presence of an inert layer under the projectingportions brings about a poor adhesion of the projecting portions, andthat presence of the inert layer gives rise to a variation of theprojection shape. It has also been found out that a change in currentdensity during plating adversely affects stability of current densityand also deforms the projection shape.

Provision of an intermediate layer of gold or the like under theprojecting portion has been also found to lead to a poorer adhesion ofthe projecting portion. Provision of such an intermediate layer has aproblem of a more complicated manufacturing process.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a probestructure which is capable of making a configuration or shape ofprojections uniform within a predetermined range and which therefore hasexcellent properties.

It is another object of the present invention to provide a method ofmanufacturing a probe structure which has projections with acomparatively uniform configuration.

Another object of the invention is to provide a probe structure whichhas projections of a good adhesion, excellent bump contacts in strengthand which rarely causes breakage to occur even after repetition ofcontact. The probe structure can keep contact resistance substantiallyconstant among individual bump contacts and is easy to manufacture.

The probe structure and the manufacturing method thereof of theinvention have the following configurations.

(Configuration 1)

A probe structure which comprises an insulating substrate having firstand second principal surfaces, a bump contact protruded from the firstprincipal surface, and an electrode electrically connected to the bumpcontact and operable as a part of an electrical circuit formed on thesecond principal surface and/or an inner side of the insulatingsubstrate, wherein the bump contact has a surface roughness which isspecified by Rmax within a range from 0.01 to 0.8 μm, Ra within a rangefrom 0.001 to 0.4 μm, and a ratio of Rmax/Ra within a range from 2 to10.

(Configuration 2)

A probe structure according to configuration 1, wherein the bump contacthas, on its surface, a plurality of projections which define the surfaceroughness and which have a projection spacing within a range from 0.1 to0.8 μm, and a projection thickness which is not smaller than one thirdof the projection spacing.

(Configuration 3)

A probe structure which comprises an insulating substrate having firstand second principal surfaces, a bump contact protruded from the firstprincipal surface, and an electrode electrically connected to the bumpcontact and operable as a part of an electrical circuit formed on thesecond principal surface and/or an inner side of the insulatingsubstrate, wherein the bump contact has, at least on its surface, aconvex/concave layer formed by an aggregation of fine grains.

(Configuration 4)

A probe structure according to configuration 3, wherein the bump contactcomprises a basic shape portion of a single layer having a base surface;the convex/concave layer being formed directly on the base surface ofthe basic shape portion to provide the surface of the bump contact.

(Configuration 5)

A probe structure according to configuration 3, wherein the bump contacthas a surface roughness which is defined by Rmax within a range from0.01 to 0.8 μm, Ra within a range from 0.001 to 0.4 μm, and a ration ofRmax/Ra within a range from 2 to 10.

(Configuration 6)

A probe structure according to configuration 3, wherein the fine grainshave a grain size within a range from 5 to 200 nm.

(Configuration 7)

A probe structure according to configuration 3, wherein theconvex/concave layer on the base surface has a hardness within a rangefrom 800 to 1,000 Hk (Knoop hardness).

(Configuration 8)

A probe structure according to configuration 4, wherein the basic shapeportion has a smooth hemispherical projection shape and a hardnesswithin a range from at least 100 Hk to up to 800 Hk.

(Configuration 9)

A method of manufacturing a probe structure, comprising the steps ofproviding a basic shape portion of a bump contact on one principalsurface of an insulating substrate; providing an electrode forming atleast a part of an electric circuit on the other principal surface ofthe insulating substrate and/or in the inside thereof; electricallyconnecting the basic shape portion of the bump contact to the electrodeforming a part of the electrical circuit; and carrying out mat platingwithout substantially exposing the base surface of the basic shapeportion to an atmosphere.

(Configuration 10)

A method according to configuration 9, further comprising the step offorming an oxidation preventing layer for preventing oxidation of thebasic shape portion, prior to the step of carrying out the mat-platingthe base surface of the basic shape portion.

(Configuration 11)

A method according to configuration 10, wherein the oxidation preventinglayer has a thickness within a range from 0.001 to 0.05 μm.

(Configuration 12)

A method according to configuration 9, wherein the mat plating iscarried out under a current density within a range from 0.1 to 1.0 A/dm²with the current density kept invariable.

(Configuration 13)

A method according to configuration 9, wherein the material for the matplating is rhodium.

(Configuration 14)

A probe structure according to configuration 4, wherein the bump contacthas a bump which is formed by the basic shape portion of nickel alone ora nickel alloy, and a mat-rhodium-plated layer on the base surface ofthe basic shape portion without any inert layer interposed between thebasic shape portion and the mat-rhodium-plated layer the probe structurebeing used for a burn-in test.

(Configuration 15)

A probe structure according to configuration 4, wherein the bump contacthas a bump formed by the basic shape portion of nickel alone or a nickelalloy and both a gold strike plating layer and a mat rhodium platinglayer on the base surface of the basic shape portion; the probestructure being used for a burn-in test.

According to configuration 1, by using a surface roughness of the bumpcontact specified by Rmax within a range from 0.01 to 0.8 μm, Ra withina range from 0.001 to 0.4 μm, and a ratio of Rmax/Ra within a range from2 to 10, it is possible to achieve an excellent durability againstrepeated contact with the device-under-test (DUT) and maintain a stablecontact resistance.

Herein, Rmax and Ra are defined by the Japanese Industrial Standard (JISB0601). Specifically, Rmax is the above-mentioned maximum height (thedistance from a highest peak to a lowest valley while Ra is theabove-mentioned center-line-mean roughness (the average of an absolutevalue of a deviation from a center line of a roughness curve to theroughness curve).

When the contact object is an aluminum electrode, an oxide film isusually formed into a thickness within a range from 0.01 to 0.1 μm. Asubstantial roughness in a roughened state is preferably defined by anRmax within a range of from 0.01 to 0.8 μm and an Ra within a range offrom 0.001 to 0.4 μm. This is because the defined roughness and thethickness on this level are sufficiently enough to break the oxide filmand to avoid damages of the electrode as a whole. A surface roughnessrepresented by Rmax less than 0.01 μm and Ra less than 0.001 μm givesonly an insufficient effect of breaking the oxide film of a metal on thecontact object even when the surface is brought into contact with theobject. With a surface roughness represented by Rmax over 0.8 μm and Raover 0.4 μm, in contrast, even the aluminum film pad is broken by theprobe structure and the electrode as the contact object is damaged.Furthermore, as the surface roughness is larger, upon pressing the bumpcontact against the contact object, the metal of the contact object isadhered to surface grooves formed among the projections and is leftthere. Under the circumstances, the surface roughness is preferablyspecified by Rmax within a range from 0.1 to 0.5 μm and Ra within arange from 0.05 to 0.25 μm.

A ratio of the above-mentioned Rmax to Ra (Rmax/Ra) exceeds 10 and thencauses an undesirable state to occur because the surface roughness iswidely varied. Specifically, undesirably high projections often appearand are weak in strength. Thus, such projections are poor in durability.A ratio of Rmax/Ra becomes smaller than 2, which results in a smallervariation of the surface roughness, but this is hardly achievable interms of manufacture. The ratio Rmax/Ra should therefore preferably beat least 2.

Even when the surface oxide film causes no problem, Rmax, Ra and Rmax/Rashould preferably be within the aforementioned ranges because a largecontact area is available, with a lower contact resistance, and a stablecontact is achieved.

According to configuration 2, the projection spacing (distance betweenprojections associated with contact) is within a range of from 0.1 to0.8 μm. The projection has a shape of a pitch or spacing that does notexceed Rmax. The projection thickness (thickness at ½ height) is atleast ⅓ the projection spacing. By satisfying these conditions, it ispossible to achieve an excellent durability against repetition ofcontact with the contact object, and to maintain a stable contactresistance. The term “projection pitch” or “projection spacing” as usedherein means the distance between centers of projections associated withcontact. The projection center may be either an apex of each projectionor a size center of a size determined by a bottom contour of theprojection.

Herein, the projection thickness is defined with reference to FIG. 2. Asingle projection is assumed to be observed on the surface condition ofa bump contact by the use of a scanning electron microscope (SEM). Inthis event, the projection thickness is defined by a size measured at ahalf height of the projection. Specifically, a curve of the half heightis drawn as a dotted line in FIG. 2 by plotting middle or half pointsbetween an apex or center of the projection to be contacted and a bottomcontour of the projection.

As mentioned in conjunction with configuration 3, when a convex/concavelayer (projections) is formed by aggregating fine grains on the surfaceof the bump contact, a maximum height of each aggregation of fine grainsis used as the apex of the projections associated with contact. Thebottom of each aggregation of the fine grains is used as the projectionbottom when the projection thickness is determined.

At any rate, a high projection density can be obtained by providing oneor more projections per μm². By obtaining a high projection density, awider contact area is available upon contact with the DUT, and thismakes it possible to obtain a stable contact resistance. The projectiondensity should preferably be within a range from at least 1 to up to 50per μm², or more preferably, from at least 1 to up to 30 per μm², orstill more preferably, from at least 1 to up to 10 per μm². Theprojection herein used means a projection associated with contact, andin the case of a convex/concave layer (projection) formed by theaggregations of fine grains as in configuration 3, each aggregation offine grains is deemed to be a single projection. An excessively highprojection density should be avoided because it leads to a smallerprojection thickness and a poorer durability of the projection.

According to configuration 3, aggregations of fine grains permitsformation of a dense film. Such a dense film can increase an areaadhered to the basic shape portion and can form a stable convex/concavelayer having a high projection density. Even when the apex portion ofthe projection itself is large in size, exposure of fine grains on thesurface makes it possible to easily break the oxide film of the contactobject.

The convex/concave layer comprising the aggregations of fine grains isformed on the surface of the bump contact without intermediary of aninert layer. This is favorable because it is possible to avoid adecrease in adhesion of the projection or variation of the projectionshape caused by the presence of an inert layer.

When the convex/concave layer is formed by using a strongly acidicplating solution on rhodium, an inconvenience may sometimes be caused byoxidation of the surface of the basic shape portion, a poorer adhesion,or non-uniform growth of the film (occurrence of variation of theprojection shape). In such a case, the inconvenience can be avoided byproviding an oxidation preventing layer for preventing oxidation of thebasic shape portion as described in configuration 10.

A convex/concave layer comprising the aggregations of fine grains may beformed on the surface of an electrode and the like which are operable asa part of an electric circuit provided on the other side, namely, thesecond principal surface of the insulating substrate. The fine grains onthe surface of the bump contact may be formed at random, or inconformity to a rule.

According to configuration 4, the aforementioned bump contact comprisesa basic shape portion of a single layer, and a convex/concave layerformed directly on the surface of the basic shape portion. As a result,it is possible to avoid deterioration of adhesion of the projectingportions caused by presence of an intermediate layer of gold or the likeunder the projecting portions, and to easily manufacture the projectingportions because of absence of an intermediate layer.

A preferable bump structure in the probe structure of the presentinvention is such that the bump contact comprises the basic shapeportion and the convex/concave layer having a surface roughness broughtabout by mat plating described later.

For the necessity to provide a hardness of the mat-plated surfacesufficient to withstand repetition of contact with the contact object onthe DUT, the hardness should preferably be within a range of from atleast 800 to up to 1,000 Hk.

According to configuration 5, the bump contact has a surface roughnessgiven by Rmax within a range from 0.01 to 0.8 μm, Ra within a range from0.001 to 0.4 μm and Rmax/Ra within a range from 2 to 10. As a result,advantages similar to those of configuration 1 are available in additionto those of configurations 3 and 4. The more preferable range of surfaceroughness of the bump contact is the same as in configuration 1.

Advantages similar to those of configuration 2 are additionallyaccomplished by satisfying the requirements of configuration 2 inaddition to those of configuration 5.

According to configuration 6, the size of the fine grains within a rangeof from 5 to 200 nm ensures availability of the advantages ofconfiguration 3.

The grain size should preferably be within a range of from 5 to 100 nm,or more preferably, from 10 to 50 nm.

The size of the grain aggregation (projection) formed throughaggregation of fine grains should preferably be within a range of from0.02 to 1 μm, or more preferably, from 0.1 to 0.4 μm.

As described as to configuration 7, the hardness of the convex/concavelayer which is the surface layer should preferably be within a range offrom 800 to 1,000 Hk.

With a hardness under 800 Hk, the surface convex/concave layer caneasily break an oxidation film upon contact with the contact object, andwith a hardness over 1000 Hk, cracks tend to occur.

The surface convex/concave layer is roughened, and should be resistantto a damage caused by repeated contact with the contact object. Theconvex/concave layer is therefore required to have a hardness higherthan the contact object. By imparting corrosion resistance andcontrollability of transfer and diffusion of the other metals from thecontact object, the contact resistance can be preferably reduced.

When a precious metal is used for the surface convex/concave layer, theprecious metal may be a single metal or an alloy thereof. In order toavoid an increase in contact resistance resulting from diffusion of abase metal throughout the entire surface and oxidation, an increase ininternal stress caused by organic impurities, and occurrence of cracks,the content of the precious metal should preferably be at least 99%. Inthe case of an alloy, a typical example is a combination ofcorrosion-resistant precious metals hardly diffusing such as rhodium andruthenium.

According to configuration 8, a hardness of the basic shape portionunder 100 Hk leads to easy deformation when the bump contact is broughtinto contact with, and pressed against, the contact object. A hardnessover 800 Hk tends to cause easy occurrence of cracks.

The material forming the basic shape portion should preferably havecrystallographic compatibility with the material of the electrodeforming a part of the electric or conduction circuit (electrodeelectrically connected to the bump contact). In addition, the materialshould also have good adhesion and hardly diffusion characteristics. Forexample, when the material for the electrode forming a part of theelectric circuit is copper, a preferable combination for the materialfor the corresponding basic shape portion is nickel or a nickel alloy.

The basic shape portion should preferably have a smooth hemisphericallyprojecting shape.

According to configuration 9, a bump contact having a strong adhesion tothe basis shape portion and a surface roughness (convex/concave layer)is obtained by carrying out mat plating without substantially exposingthe surface of the basic shape portion to an atmosphere (for example, bycontinuously carrying out plating).

The process of applying mat plating to the surface layer withoutsubstantially exposing the basis shape portion to the atmosphere is, forexample, a process of preventing the bump contact from contacting withthe atmosphere during a predetermined period. The predetermined periodlasts from forming the basic shape portion by plating up to applicationof mat plating to the surface layer. More specifically, the processcomprises the steps of setting an insulating substrate on a jig, puttingthe same in a plating vessel, forming a basic shape portion by plating,then, rinsing off the plating solution, used for forming the basic shapeportion, adhering to the plating jig while taking out the jig from theplating vessel for the next step of surface layer plating, andcontinuously spraying pure water onto the bump contact prior to matplating of the surface layer and before and after the treatment so thata water film always covers the bump contact. Thus, the bump contact isprevented from being in contact with the atmosphere during the periodfrom the end of forming of the basic shape portion through entrancethereof in the plating solution for mat plating. The bump contact is notallowed to come into contact with the atmosphere not only by means ofthe water film, but also during the step of surface activation of thebasic shape portion through a sulfate treatment. When two kinds ofplating are carried out in succession in the same vessel, as well, purewater is always continuously sprayed onto the bump contact during risingof the plating solution, the plating pretreatment, and rinsing, so as toprevent the bump contact from coming into contact with the atmosphere.

The mat plating means a plating which is effective to achieve a surfacecondition in which the surface is not glossy and not smooth, and has aproperty of diffused reflection rather than mirror surface reflection.

When the bump contact of the basic shape portion is exposed to theatmosphere prior to forming a surface layer plating film, the surface ofthe contact is in inert state, and this deteriorates adhesion with thesurface layer plating formed in the following step. This inert conditionof the contact surface is considerable particularly when using nickel ora nickel alloy, and activation through a pretreatment is difficult.

By applying mat plating without exposing the surface of the basic shapeportion to the atmosphere, strong adhesion between the differentmaterials is ensured, and this gives a plating film which hardly comesoff even after repeated contact with the contact object.

In order to prevent the surface of the basic shape portion from beingexposed to the atmosphere, as in configuration 10, an oxidationpreventing layer for preventing oxidation of the basic shape portion maybe formed prior to mat plating. When the oxidation preventing layer isthick, a decrease in adhesion of the projection or variation of theprojection shape would be produced. The thickness should therefore bethe smallest possible. As in configuration 11, the thickness of theoxidation preventing film should preferably be within a range of from0.001 to 0.05 μm. Methods of forming an oxidation preventing film havinga thickness of this order include stroke plating. The material for theoxidation preventing film should be gold, silver or palladium.

Particularly, when the material for the convex/concave layer is rhodiumformed with a strongly acidic plating solution, the surface of the basicshape portion may be oxidized, adhesion may be deteriorated, or the filmgrowth may become non-uniform (variation of the projection shape may beproduced), even if the surface is not substantially exposed to theatmosphere. Formation of the oxidation preventing film is thereforeeffective.0

According to configuration 12, by forming the surface convex/concavelayer with a relatively low plating current density (specifically,within a range of from 0.1 to 1.0 A/dm²), it becomes easier to controlthe surface roughness condition. Even when providing a plurality of bumpcontacts on a substrate, therefore, it is possible to make the surfacecondition of each bump contact closer to a uniform state, and reducevariation of contact condition between the contact object and each bumpcontact.

By always keeping a current density of mat plating constant, the currentdensity is stabilized, and variation of the projection shape is neverproduced.

By varying the current density, the amount of polishing agent, and theplating material in the plating step, furthermore, it is possible tocontrol the surface roughness condition and the projection density, andachieve a surface roughness suitable to break through the oxide film ofthe electrode section.

According to configuration 13, rhodium used as the material for matplating gives strong adhesion, and makes it difficult for the platingfilm to come off even after repeated contact with the contact object. Byvarying the current density, the amount of polishing agent, and theplating material in the plating step, it is possible to accuratelycontrol the surface roughness condition and the projection density.

According to configuration 14, contact resistance can be kept low fromthe initial stage of contact, and also can be maintained at a low leveleven upon the lapse of a period of time in a heated state. This is veryeffective when a burn-in test is carried out, in addition to theadvantages described as to configurations 1 to 8. In this case, a bumpis subjected to mat rhodium plating on the surface of the basic shapeportion of nickel alone or a nickel alloy. No inert layer is depositedin the bump.

Similarly, as in configuration 15, by having a bump subjected to goldstrike plating and mat rhodium plating on the surface of the basic shapeportion of nickel alone or a nickel alloy, contact resistance is lowfrom the initial stage of contact, and contact resistance can bemaintained at a low level even upon the lapse of a period of time evenin a heated state. This is effective on carrying out the burn-in test,in addition to the advantages described as to configurations as toconfigurations 1 to 8. For the purpose of simplifying the manufacturingprocess, configuration 14 is preferable. However, on using a stronglyacidic plating solution such as that in mat rhodium plating, it ispossible to ensure prevention of oxidation of the surface of the surfacelayer of nickel alone or a nickel alloy, and avoidance of a decrease inadhesion of the projections or variation of the projection shape. Thisresults in an improved reliability.

According to the present invention, it is possible to limit thevariation in contact resistance to up to 1 Ω after contacts are repeated300 times.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view for describing a conventional probestructure;

FIG. 2 illustrates the projection thickness of the surface condition ofthe lump contact;

FIG. 3 is a partial sectional view for describing the probe structure ofan embodiment of the present invention;

FIG. 4 is a partial sectional view for describing the probe structure ofanother embodiment of the invention;

FIGS. 5A to 5C are partial sectional views for describing themanufacturing process of the probe structure of an example of theinvention;

FIG. 6 is an SEM photo of the bump portion in the probe structuremanufactured in an example of the invention;

FIG. 7 is an enlarged SEM photo of the bump surface in a probe structuremanufactured in an example of the invention;

FIG. 8 illustrates the relationship between resistance and the number ofcontacts in a probe structure manufactured in an example of theinvention; and

FIG. 9 is a schematic view for describing a burn-in test in an exampleof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The probe structure and the manufacturing method thereof of the presentinvention will now be described in detail.

FIG. 3 is a sectional view schematically illustrating the probestructure, together with the manufacturing method thereof. In the probestructure shown in FIG. 3, a bump contact 2 is provided on one side,namely, a first principal surface of an insulating substrate 1. On theother hand, an electrode 3 which is operable as a part of an electric orconduction circuit is provided on the other side, namely, a secondprincipal surface of the insulating substrate 1. A throughhole 5 isformed in the insulating substrate 1. The bump contact 2 and theelectrode 3 operable as the part of the electric circuit are arranged onopposite sides or principal surfaces of the insulating substrate and areelectrically connected to each other via a conduction circuit 4 formedby a conductive material placed within the throughhole 5. The bump 2comprises a hemispherical basic shape portion 2 a and a surface layer 2e having a roughened surface. In the example shown in FIG. 3, the basicshape portion has a single-layer structure, and a surface layer 2 eroughened by mat plating is formed on the surface of the basic shapeportion 2 a. In the example shown in FIG. 4, an oxidation preventinglayer is formed on the surface of the basic shape portion 2 a to form amulti-layer structure, and a surface layer 2 e roughened by mat platingis formed on the surface of the oxidation preventing layer. The surfacelayer 2 e roughened by mat plating is formed through aggregations ofrandomly formed fine grains.

The insulating substrate is not limited to a particular one so far as itis formed by an electrical insulator, but should preferably be flexibleas well. Specifically, it may be selected from the group consisting ofpolyimide resins, polyester resins, epoxy resins, urethane resins,polystyrene resins, polyethylene resins, polyamide resins, ABS resins,polycarbonate resins and silicone resins, irrespective of eitherthermosetting or thermoplastic resins, according to the purpose of use.Among these resins, a polyimide resin excellent in heat resistance andchemical resistance and displaying a high mechanical strength ispreferable. A thickness may be arbitrarily selected for the insulatingsubstrate. In order to achieve sufficient mechanical strength andflexibility, however, the thickness should usually be within a rangefrom 2 to 500 μm, or preferably, from 10 to 150 μm. As a probe structureused in a burn-in board or a probe card, an insulating resin film havinga thickness of about 10 to 50 μm is preferable.

The electrode forming a part of the electric circuit is formed at aposition corresponding to the interior point or the back of the positionwhere a bump contact is to be formed in the insulating substrate. Theelectrode is electrically connected to the bump contact. The electriccircuit comprises, apart from a circuit pattern formed of conductors andsemiconductors, component elements forming the circuit such as contacts,coils, resistors and condensers. The electric or conduction circuit maybe formed externally to the insulating substrate (for example, a circuitboard). There is no particular restriction on the material for theconduction circuit and the electrode forming a part thereof,irrespective of a conductor or a semiconductor, so far as it isconductive. A known conductive metal is preferable. Applicable metalsinclude single metals such as copper, gold, silver, platinum, lead, tin,nickel, iron, cobalt, indium, rhodium, chromium, tungsten, andruthenium, and alloys containing any of these metals such as a solder,nickel-tin and gold-cobalt. A lamination structure may be formed byusing two or more from these metals and alloys. The thickness of theconduction circuit or the electrode forming a part thereof is notlimited.

For the formation of the conduction circuit and the electrode forming apart thereof, a method comprises the steps of forming a conductivematerial layer on the entire surface of the insulating substrate, andremoving portions other than a circuit pattern portion to be formed byetching or the like.

No particular limitation is imposed on the diameter of the throughholefor ensuring communication between the electrode forming a part of theconduction circuit and the bump contact. A larger diameter to the extentthat the boundary between neighboring throughholes is not broken ispreferable because it corresponds to a smaller electric resistance atconducting portions.

The diameter of the throughhole should practically be within a range offrom 5 to 200 μm, or particularly, from 10 to 80 μm. The throughholesmay be formed by any of laser processing, photolithographic processing,chemical etching using a resist having a chemical resistance differentfrom that of the insulating substrate, plasma processing, and mechanicalprocessing such as punching. Among others, laser processing usingexcimer laser, carbon dioxide gas laser, or YAG laser, which permitsfine processing of a throughhole with arbitrary diameter and interholepitch, is preferable because of the capability to cope with therequirement of fine pitching of the bump contact. The posture of thethroughhole relative to the surface of the insulating substrate is notlimited to right angles, but the throughhole may be formed so as to beinclined at a prescribed angle to the surface of the insulatingsubstrate. In this event, conduction between the electrode and the bumpcontact should be ensured in a slightly shifted positional relationshipwith each other.

The conducting section may be formed in the throughhole to electricallyconnect the contact to the electrode forming a part of the conductioncircuit. The part may be formed either by filling the throughhole with aconductive material, or by depositing a layer of a conductive materialon the wall surface of the throughhole as in throughhole plating. Theconducting section may be formed by a film forming method such as theelectrolytic plating method or the electroless plating method or the CVDprocess, or a method of mechanically fitting a conductive material intothe throughhole. Among others, a method of exposing the electrodeforming a part of the conduction circuit in the throughhole, and fillingthe throughhole with the conductive material by electrolytic plating byusing the electrode as a negative pole, since this method ensureselectric conduction and is simple.

The basic shape portion of the bump contact may have a convex, concaveor any other shape in consideration of the shape of the contact object,irrespective of whether or not it projects from the insulating substratesurface. As in the case of the known bump contact, a smoothhemispherically projecting one is the most useful. The hemisphericalshape as used herein is not limited to a perfect hemisphere, butincludes projecting shape with a smooth and monotonous curve.

The manufacturing method of the basic shape portion, though not setforth in the invention, should preferably comprise the following steps.

The manufacturing method in the case where the basic shape is of thesingle-layer structure will be described.

A position where a bump contact is to be formed is determined on thesurface of an insulating substrate, and an electrode forming a part of aconduction circuit is formed at a position in the interior or on theback of the substrate corresponding to the determined position. Athroughhole is opened at a position where the bump contact is to beformed, and the electrode forming a part of the conduction circuit isexposed on the bottom of this throughhole. The throughhole is openedfrom the first principal surface of the insulating substrate and reachedto the electrode formed on the second principal surface. The throughholeis filled with a conductive material deposited by electroless plating.Such plating is carried out with the electrode given a negative voltageso as to form a conducting section. The deposition is continued by usingthe same material as this conductive material also for the bump contact.As a result, a smooth hemispherical projection grows from the firstprincipal surface of the insulating substrate and serves as a basicshape portion of the bump contact. In the above-mentioned steps, aconcave portion relative to the surface of the insulating substrate maybe formed as a basic shape portion by discontinuing deposition prior tofilling the throughhole with the conductive material. The basic shapeportion should preferably be of a single structure (single-layerstructure) by causing deposition of only one material to occur with aview to achieving adhesion between materials and facilitatingmanufacture.

Then, as shown in FIG. 3, an embodiment in which the basic shape portionhas a single-layer structure will be described. The bump contact 2 shownin FIG. 3 comprises the basic shape portion 2 a and a surface layer 2 eand has a double-layer structure.

As in the known bump contact, the basic shape portion is connected tothe electrode via the conducting section, and serves as a core in thesurface layer of the bump contact to support the strength of thecontact. The basic shape portion should have a hardness within a rangefrom at least 100 to up to 800 Hk (Knoop hardness), or preferably, from200 to 600 Hk, or more preferably, from 300 to 600 Hk. With a hardnessof under 100 Hk, the bump contact tends to deform upon contact with, andpressing against, the contact object. With a hardness of over 800 Hk,cracks tend to easily occur. The material for forming such a basic shapeportion is not particularly limited, but an inexpensive conductive metalused for the known bump is preferable, including, for example, nickel,nickel-tin alloy, nickel-palladium, and copper.

The material for forming the basis shape portion should preferably becrystallographically compatible with the material for the conductioncircuit, have a high adhesion, and is low in diffusion. When thematerial for the conduction circuit is copper, nickel or a nickel alloyleads to a preferable combination as a material for the basic shapeportion.

The surface convex/concave layer is roughened. It is susceptible to adamage by the repeated contact with the contact object, and is thereforerequired to have a higher hardness than the contact object. The contactresistance can be kept at a low level by imparting corrosion resistance,and controllability of transfer and diffusion of other metals from thecontact object. The surface layer should preferably have a hardnesswithin a range of from at least 800 to up to 1,000 Hk, or morepreferably, from 850 to 1,000 Hk, or particularly more preferably, from900 to 1,000 Hk. With a hardness of under 800 Hk, the convex/concavelayer tends to be easily damaged upon contact with the conductor of theDUT. With a hardness of over 1000 Hk, on the other hand, cracks tend toeasily occur. Preferable materials for the surface convex/concave layerare corrosion-resistant metals having a property as a barrier preventingmetals from transferring and diffusing from the contact object,including such precious metals as rhodium, ruthenium, cobalt, chromiumand tungsten.

When using a precious metal for the surface convex/concave layer, theprecious metal may be a single metal or an alloy. The content of theprecious metal should preferably be at least 99% in consideration ofavoiding an increase in contact resistance caused by oxidation of basemetals diffusing to the surface, an increase in internal stress causedby organic impurities, and occurrence of cracks. When using an alloy, acombination of precious metals for ensuring corrosion resistance and forreducing diffusion may be, for example, a combination of rhodium andruthenium. The thickness of surface convex/concave layer shouldpreferably be such that wear resistance of the contact object orelectrode in the DUT can be assured.

A multi-layer structure in which an oxidation preventing layer is formedon the surface of the basic shape portion 2 a can be manufactured onlyby adding the step of forming the oxidation preventing layer between theformation of the basic shape portion 2 a and the formation of thesurface convex/concave layer. The remaining steps may be the same asthose in the above-mentioned manufacturing method. The oxidationpreventing layer is helpful to avoid a reduction in adhesion of thesurface convex/concave layer (projection) or to suppress variation ofthe projection shape through oxidation of the basic shape portion. Thematerial for the oxidation preventing layer suffices to be other thanthe material formed by a strongly acidic plating solution. A stronglyacidic plating solution oxidizes the basic shape portion during the stepof forming on the surface of the basic shape portion. Availablematerials may be, for example, gold, silver and palladium which can beplated by the use of weak acid plating solution, neutral platingsolution, or alkali plating solution. A thick oxidation preventing layertends to cause a decrease in adhesion of the projection or variation ofthe projection shape to occur. The thickness should therefore preferablybe within a range of from 0.001 to 0.05 μm, and the forming methodincludes, for example, strike plating.

EXAMPLES

(Probe structure having a single-layer basic shape portion)

Example 1

The present invention will now be described more in detail by means ofexamples. In this example, the bump contact structure shownschematically in FIG. 3, i.e., a probe structure having a bump contactwith a surface-roughened surface layer (convex/concave layer) formedthereon by continuous mat plating (used for wafer-level burn-in test)was actually manufactured. In other words, the illustrated bump contactmay be assembled within a semiconductor tester.

More specifically, as shown in FIG. 5A, use was made of a double-layerfilm (for example, ESPERFLEX made and sold by Sumitomo Metal Mining Co.,Ltd.; polyimide film having a thickness of 25 μm and a copper foilthickness of 16 μm) which has a commercially available polyimide film 11and copper foil 13 affixed together. Subsequently, a KrF excimer laser(wavelength: 248 nm) was irradiated to a position where a bump contactwas to be formed in the polyimide film 11 as shown in FIG. 5B, and athroughhole 15 having an inside diameter of 30 μm was formed. The copperfilm 13 was exposed on the bottom of this throughhole.

Then, plasma ashing was applied to remove carbon adhering to thepolyimide surface upon throughhole processing by excimer laser andimprove wettability of the polyimide surface to the plating solution.

Then, after protecting the copper foil surface on the upper side frombeing plated, the plating electrode was connected to a part of thecopper foil 13, and electro-plating of a nickel alloy was conducted withthe copper foil exposed in the throughhole 15 as a negative pole. Morespecifically, as shown in FIG. 5C, the process comprised the steps offilling the throughhole 15 with deposited nickel alloy, continuingdeposition, causing growth to a height projecting by 25 μm from thepolyimide surface into a hemispherical single-layer basic shape portion12 a, transferring this basic shape portion 12 a made of a nickel alloyto the water rinsing step so as not to allow the basic shape portion 12a made of the nickel alloy to come into contact with the atmosphere,water-rinsing the same, then activating the surface of the basic shapeportion with a 5% sulfuric acid treatment, water-rinsing the same again,then after water rinsing, setting a plating current density of 0.5A/dm², and mat-rhodium-plating while always maintaining a constantplating current density. For a period from plating start of nickel alloythrough the end of mat rhodium plating, water rinsing and a pretreatmentwere carried out without allowing the basic shape portion to come intocontact with the atmosphere in succession with no time interval(continuous mat rhodium plating).

The continuous mat rhodium plating deposits a rhodium layer to athickness of 2 μm. As a result, a surface roughness conditionrepresented by an Rmax of 0.5 μm, an Ra of 0.1 μm and an Rmax/Ra of 5was obtained. The surface roughness was measured by a probe-based methodby measuring an actual bump surface by means of a surface shapemeasuring device (manufactured by Tencor Instruments Co.: TENCOR P2).

Finally, the copper foil 13 was patterned through etching to form anelectric or conduction circuit and an electrode forming a part thereof(not shown), and a probe structure as shown in FIG. 3 was obtained.

Observation of the surface condition of the bump contact by an SEM(scanning electron microscope) revealed that, as shown in FIGS. 6 and 7,aggregations of fine grains at random formed convex and concave portionson the surface of the bump contact. A measurement of the grain size gavea size within a range of from 5 to 200 nm, with an average grain size of80 nm. Each projection formed by aggregations of grains had a sizewithin a range of from about 0.3 to about 0.6 μm, and the projectiondensity was as represented by 1 to 7 grains per μm². The projections hada thickness within a range of from about 0.1 to about 0.3 μm and aprojection pitch within a range of from about 0.25 to about 0.6 μm,suggesting that the projection thickness was about ⅖ to about ½ (atleast ⅓) of the projection pitch.

A tape peeling test was carried out by the use of an adhesive tape (forexample, one made by Nichiban Co.: CELLOTAPE) showed that the continuousmat rhodium plating layer did not peel off.

The hardness of the basic shape portion made of the nickel alloy and thecontinuous mat rhodium plating layer was measured by means of amicro-Vickers hardness meter, and this gave a hardness of 600 Hk and 900Hk, respectively.

Comparative Example 1

After forming a bump contact from a nickel alloy, and leaving the samefor ten minutes in the atmosphere, mat rhodium plating was performed(non-continuous mat plating) in the same manner as in Example 1. As aresult, the bump contact had a surface roughness as represented by anRmax of 1.0 μm, an Ra of 0.02 μm and an Rmax/Ra of 50. Analysis of thebump obtained from the non-continuous mat plating permitted confirmationof the presence of an inert condition comprising nickel oxide betweenthe nickel alloy and the rhodium layer. This resulted in variation ofadhesion of rhodium grains to the surface of nickel alloy, and Rmax/Ralargely exceeded 10. As a result, the adhesion of the rhodium layer as awhole became poorer. Repetition of contact with the contact objectcaused occurrence of cracks and chipping of the surface rhodium layer,and this led to a seriously decreased durability. A large height of theprojection sometimes led to a thinner projection. Repeated contactbetween the bump contact and the contact object caused easy peeling fromthe bump surface and hence a change in contact resistance. It wasfurthermore difficult to form the product while always keeping constantfine projection height (surface roughness), variation of roughness, andprojection density, and the contact resistance dispersed in some casesbetween bumps.

A tape peeling test carried out with an adhesive tape (for example, madeby Nichiban Co.: CELLOTAPE) showed easy peeling of the rhodium layer.

Examples 2 to 5 and 8 to 10, and Comparative Examples 2 to 5

A probe structure having bump contacts of which the surface roughnesswas different from each other was prepared in the same manner as inExample 1, except that the plating current density and the amount ofglossing agent were appropriately adjusted in the continuous mat rhodiumplating step. Measurement of the bump surface roughness, Rmax/Ra andgrain size gave results as shown in Table 1.

TABLE 1 Rmax Ra Grain Size (μm) (μm) Rmax/Ra (nm) Example 2 0.01 0.00128.33 5-100 Example 3 0.8 0.13 6.15 10-200  Example 4 0.01 0.001 10.05-100 Example 5 0.8 0.4 2.0 10-200  Example 8 0.12 0.05 2.4 5-200Example 9 0.3 0.07 4.29 5-200 Example 10 0.5 0.2 2.5 5-200 Comparative0.01 0.0007 14.3 5-100 Example 2 Comparative 0.82 0.02 41 10-200 Example 3 Comparative 0.009 0.0008 11.3 5-100 Example 4 Comparative 0.80.42 1.9 15-200  Example 5

Examples 6 and 7 and Comparative Examples 6 and 7

Probe structures were prepared in the same manner as in Example 1 exceptthe plating current density was set at 0.1 A/dm² (Example 6), 1.0 A/dm²(Example 7), 0.05 A/dm² (Comparative Example 6), and 1.5 A/dm²(Comparative Example 7). Measured results of surface roughness, Rmax/Raand grain size were as shown in Table 2.

TABLE 2 Rmax Ra Grain Size (μm) (μm) Rmax/Ra (nm) Example 6 0.01 0.0052.0  5-100 Example 7 0.8 0.09 8.8 10-200 Comparative 0.004 0.001 4.0 5-200 Example 6 Comparative 1.5 0.06 25.0 10-200 Example 7

Evaluation of Contact Condition

An aluminum chip comprising a glass substrate and an aluminum layervapor-deposited thereon into a thickness of 1 μm was used as an contactobject, and the contact condition of probe structures having differentvalues of surface roughness as above was evaluated. When the surfacelayer formed by continuous mat rhodium plating had a surface roughnessas represented by an Rmax within a range of from 0.01 to 0.8 μm, an Rawithin a range of from 0.001 to 0.4 μm, and an Rmax/Ra within a range offrom 2 to 10 (Examples 1 to 10), the aluminum oxide film wasappropriately broken. Under a load of 1.0 g per bump, a low contactresistance of up to 1 Ω was obtained, and contribution to stabilizationof contact resistance could be confirmed.

As a result of evaluation of 300 times under a load of 10 g against thecontact object, the bump contacts on which the rhodium layer was formedby non-continuous mat plating showed cracks and chipping of the rhodiumlayer after only one to two runs of contact. In the samples in which arhodium layer was formed by continuous mat plating, and no decrease incontact resistance was observed (FIG. 8). The surface condition of thebump contacts in which no cracks or chipping were caused by therepetition of contact was observed through a microscope for evaluation.When the surface layer formed by continuous mat plating had a surfaceroughness as represented by an Rmax within a range of from 0.01 to 0.8μm, an Ra within a range of from 0.001 to 0.4 μm, and an Rmax/Ra withina range of from 2 to 10 (Examples 1 to 10), the projections of thesurface layer showed no deterioration.

Using the probe structures obtained in the above-mentioned Examples 1 to10, a contact repeating test on the aluminum chip was carried out. Theresult revealed that wear and chipping of the surface were far slighterthan in the conventional art, and a highly reliable contact conditioncould be kept for a longer period of time.

In Comparative Examples 3, 5 and 7, on the other hand, the large surfaceroughness caused penetration through the aluminum film which was theDUT, and damaged the electrode. In Comparative Examples 2, 4, 3, and 7,the large variation of the surface roughness (Rmax/Ra) caused chippingof the projections at high portions and other deterioration afterrepetition of contact. Especially, it was observed in ComparativeExamples 3 and 7 that a lot of projections were chipped off.

In Comparative Examples 2, 4 and 6 in which the surface roughness waslow, bringing the bump into contact with the DUT gave only a limitedeffect of breaking through the metal oxide film, and variation ofcontact resistance between different bump contacts was produced.

In Comparative Examples 6 and 7, in which plating was carried out with acurrent density largely deviating from an appropriate current densityfor rhodium plating, deposition of rhodium was not stabilized, andgrains grew larger in size to over 200 nm at portions other than thepoints where surface roughness had been measured, resulting in a verylarge surface roughness. Thus, bumps suffered from abnormal depositionof plating film.

Comparative Example 8

Current density was varied upon carrying out continuous mat rhodiumplating, and a probe structure having a bump contact shown in FIG. 1 wasobtained.

As a result, it was ascertained that varying the current density duringplating caused an unstable current density and produced variation of theprojection shape.

Comparative Example 9

A probe structure was prepared in the same manner as in Example 1 orComparative Example 1 except that an intermediate layer (1 μm)comprising a gold plating layer was provided on the surface of the basicshape portion made of nickel alloy, and continuous or no-continuous matrhodium plating was applied to the surface thereof.

As a result, the rhodium plating showed a low adhesion and peeled off(multi-layer probe structure in which an oxidation preventing layer wasformed on the surface of the basic shape portion).

Example 11

A probe structure (applicable for burn-in test purposes) wasmanufactured in the same manner as in Example 1 except that, afterforming a basic shape portion 12 a as in Example 1, an oxidationpreventing layer was provided by Au (gold) strike plating carried out bythe use of weak acid Au (gold) plating bath. The Au strike platingconditions included a film thickness of up to 0.05 μm. As a result,aggregation of randomly formed fine grains formed irregularities on thesurface of the bump contact. The surface roughness was represented by anRmax of 0.4 μm, an Ra of 0.1 μm, and an Rmax/Ra of 4, with grain sizesranging from 10 to 150 nm and an average grain size of about 100 nm. Atape peeling test was carried out by use of an adhesive tape (forexample, made by Nichiban Co.: CELLOTAPE). The continuous mat rhodiumplating layer did not peel off. In an evaluation test conducted on thesame contact condition as above (evaluation on repetition of 300 runsunder a load of 10 g on the contact object), resistance was constant atabout 0.45 Ω.

Example 12

A burn-in test (Japanese Unexamined Patent Application Publication No.7-231019) was carried out by the use of a wafer-level burn-in tester asillustrated in FIG. 9. Specifically, the tester is manufactured bypreparing a membrane ring 10 having a probe structure which may besimilar to that shown in the above-mentioned example and which is formedon a polyimide film 11 deployed within the ring 10 and supported on aring 16, as shown in FIG. 9. On testing an Si wafer 40 placed on avacuum chuck (not shown), the membrane ring 10, an anisotropicconductive rubber sheet 20, and a glass multi-layer circuit board 30were arranged in this order on the Si wafer 40 (having an electrode padmade of aluminum). Under the circumstances, the entire assembly wassucked and fixed and all the devices on the wafer 40 were connected tothe glass multi-layer circuit board 30 via a print board to a testmachine. The burn-in test was carried out by increasing the temperaturefrom the room temperature to a set temperature within a range of from 80to 150° C.

It is to be noted that the illustrated multi-layer circuit board 30 hadan insulating layer and a plurality of conductive patterns which wereformed on front and rear surfaces of the insulator layer and which wereelectrically connected to each other through contact holes opened at theinsulating layer.

As a result, the bump made of nickel alloy having a continuous matrhodium plating layer, manufactured by the manufacturing method of theexample had a low contact resistance from the initial stage of contact,and the low contact resistance was maintained after the lapse of aperiod of time even in a heated state. The continuous mat rhodiumplating produced a strong adhesion of the projections. The projectionswere excellent in strength, hardly suffered deterioration from repeatedcontact, and were free from variation of contact resistance betweendifferent bump contacts.

The bump comprising nickel alloy tended in contrast to show a decreasein contact resistance upon the lapse of time in a heated state.

The bump that was made of nickel alloy having a gold plating film(thickness: 1 μm) (Comparative Example 9) had a low contact resistanceat the beginning of contact, but tended to exhibit an increase incontact resistance with time in a heated state.

The bump prepared by providing an intermediate layer (thickness: 1 μm)comprising a gold plating film on the surface of a bump made of nickelalloy, and applying continuous or non-continuous mat rhodium plating tothe surface thereof showed a poor adhesion of rhodium which peeled off.

These findings suggest that the bump prepared by applying continuous matrhodium plating to the surface of a bump made of nickel alloy issuitable for use for burn-in test purposes.

The present invention is not limited to the aforementioned examples.

For example, a buffer layer serving to absorb and alleviate the stressproduced in the contact by a contact pressure upon pressurizing thesurface layer upon inspection may be provided between the basic shapeportion and the surface layer having a prescribed surface roughness.Applicable materials for the buffer layer include gold, palladium,silver, indium and platinum. It is however necessary to pay attention topeeling and variation of surface irregularities.

The roughness of the bump surface can be appropriately set by varyingthe electrode pad or the circuit pattern, in consideration of thethickness of the contact object on the DUT or the thickness of the oxidefilm on the conductor surface.

The prescribed roughness of the bump surface may be achieved by anymethod other than the appropriate adjustment of the plating currentdensity or the amount of the glossing agent as in the above-mentionedexamples. Applicable methods include, for example, a method ofdispersing fine particles of diamond or the like in the basic shapeportion or the surface layer and forming irregularities (projections) inthe surface layer at the contact portion, a method of dispersing suchfine particles, then, removing the fine particles in the proximity ofthe surface through etching or the like, and forming irregularities(projections) in the surface layer at the contact portion, and a methodof mechanically forming irregularities by bringing the contact portionof the surface layer into contact with a material having a rough surfaceor with fine particles of powder.

According to the present invention, it is possible to provide a probestructure having excellent properties, of which the projection shape iswithin an appropriate range, and a manufacturing method thereof.

According to the invention, furthermore, it is possible to provide aprobe structure in which the projections have a strong adhesion and areexcellent in strength, which suffers from only slight deterioration evenafter repetition of contact, of which the contact resistance does notdisperse between bump contacts, and which permits easy manufacture, anda manufacturing method thereof.

Although description has thus far been made about the case where theprobe structure according to the invention is used for the wafer-levelburn-in test, the probe structure according to the invention may be usedfor testing a chip size package (CSP), or as a tape carrier for achip-level burn-in test, a burn-in probe card, a membrane probe card.

What is claimed is:
 1. A probe structure which comprises an insulatingsubstrate having first and second principal surfaces, a bump contactprotruded from the first principal surface, and an electrodeelectrically connected to the bump contact and operable as a part of anelectrical circuit formed on the second principal surface and/or aninner side of the insulating substrate, wherein: said bump contact has asurface roughness which is specified by Rmax within a range from 0.01 to0.8 μm, Ra within a range from 0.001 to 0.4 μm, and a ratio of Rmax/Rawithin a range from 2 to
 10. 2. A probe structure according to claim 1,wherein said bump contact has, on its surface, a plurality ofprojections which define said surface roughness and which have aprojection spacing within a range from 0.1 to 0.8 μm, and a projectionthickness which is not smaller than one third of the projection spacing.